A Time of Giants: Remembering Robert 'Bob' Skeel and the Impactful Numerical Analysis Group

12/15/2021 3:57:44 PM Aaron Seidlitz, Illinois CS

Learning of their former colleague’s recent death gave people throughout the Illinois CS community a chance to recall the impression Skeel left from a career here that spanned 30 years.

Written by Aaron Seidlitz, Illinois CS

Hearing of former Illinois Computer Science professor Robert “Bob” Skeel’s recent passing at the age of 73, has saddened many of his former colleagues and students who knew him well.

Robert "Bob" Skeel
Robert "Bob" Skeel

However, it has also presented an opportunity for those same people to recall his impact – achieved through technically brilliant research accomplishments and a calm, rational and helpful demeanor.

Skeel was a faculty member at Illinois CS from 1974-2004, and his presence here traces back to the origin of the department. Stemming from a reorganization of the Digital Computer Laboratory (DCL) – when elements from math, electrical engineering, and physics merged into one entity – the Illinois CS department began in 1964.

That same year was Abraham H. Taub’s final as DCL head, and one of his PhD students was C. William Gear – a pioneer in numerical analysis and later CS Department Head.

The numerical analysis group grew under Gear’s influence, and one of the people added to the faculty was Skeel. A core group of Illinois CS faculty grew out of this effort, influencing almost all areas of computing research conducted here.

The next stage of growth for this group included another longtime professor, Michael T. Heath, who worked closely with Skeel.

“When I came here in 1991, there was a large group of faculty, including Bob Skeel. I learned quickly that we had quite a bit in common,” Heath said. “We taught some of the same courses, we did qualifying exams together and served on thesis committees for each other’s students.

“I joined a very prestigious group, and I like to think I contributed some to the reputation myself. But because of people like Bob, that was undoubtedly a golden era.”

Citing the influence of these remarkable scientists, current Illinois CS Department Head Nancy M. Amato believes numerical analysis – now included in a research area called Scientific Computing – remains an integral part of the department.

"I recall Bob from my time as a student – that sure was a time of giants in numerical computing for the department,” Amato said.  "Those faculty provided the foundation for our strength in the area that persists until today, which, in turn, is an important cornerstone for the overall strength of our program."

Calling Skeel a “first-rate theoretician,” Heath was also impressed with his former colleague’s ability to push himself beyond that capability and into practical applications.

Skeel, here pictured in his office, was influential through his expertise in numerical analysis, but he also dove into application-based projects, too.
Skeel, here pictured in his office, was influential through his expertise in numerical analysis, but he also dove into application-based projects.

“I respected the fact that Bob was willing and able to roll up his sleeves on real world problems,” Heath said. “Bob proved some very interesting theorems, which I often cited in my own classes to show the students that CS at Illinois was an important contributor to the body of knowledge they were learning.

“But he also dove right into the NAMD project, which produced one of the world’s leading efforts – possibly the foremost effort – into parallel code for molecular dynamics.”

Work on this project came through an interdisciplinary team that became known as the Theoretical and Computational Biophysics Group founded at the Beckman Institute. It included Skeel and Laxmikant “Sanjay” Kale from Illinois CS and physicist Klaus Schulten who worked through Beckman Institute.

Kale called it the “most successful example of interdisciplinary work” that he’s been a part of during his career.

“Bob’s abilities in numerical analysis stand on their own, but he also possessed keen insights to formulate novel and up-to-date arguments around coding and programming languages,” Kale said. “ Klaus was already very well established in molecular simulations, to the point that his advisor later received a Nobel Prize for work in this area. And Bob made some unique contributions to the numerical methods that went into NAMD, for example advocating symplectic integrators for long-term energy conservation.”

“It was amazing to bring all of our different skills, expertise and reach from our various communities together to target a parallel, object-oriented molecular dynamics code designed for high-performance simulation of large biomolecular systems.”

Kale and Heath both said that Skeel was a man of few words, but he made those words count.

Another former colleague of his, and Illinois CS professor from 2003-2010, Stephen Bond said that he first met Skeel at a conference. The two had a mutual colleague and that initial interaction turned into a further connection when Bond was a postdoc at University of California, San Diego. At the same time, Skeel took sabbatical there.

Bond, now Senior Member of Technical Staff with Sandia National Laboratories, recalled how Skeel became instrumental to his starting at Illinois CS. Their working relationship went so well it continued nearly until the time of Skeel’s death.

“Bob was always very kind, especially to people less established in the field,” Bond said. “He was always very encouraging to students and junior faculty, especially when he was impressed by their presentations and research. Everything he did was in the long-term best interest of the group and his students. And people listened to him.

“In March 2020, he visited me at Sandia and gave a well-attended presentation on more recent research with many former Illinois CS students who are now working at Sandia in attendance.”

Skeel is survived by his wife Marjorie, two daughters, their spouses, and four grandchildren. A private family memorial service was held on November 5 at Christ Church Anglican in Phoenix. A full obituary can be found here.

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This story was published December 15, 2021.